Living with helicopter noise : evaluating sound insulation techniques for domestic dwellings using real helicopters

Specific remedial works designed to improve sound installation and reduce the noise level produced by helicopters inside dwellings are described. The theoretical problems and practical solutions to installing high performance acoustic insulation to a traditional property in the UK are presented. A novel application of ISO 140-5 is presented using real helicopters to measure sound insulation in-situ in the presence of multiple flanking transmission paths. Dedicated field trials to evaluate the performance of such acoustic double-glazing and associated modifications systems were performed and the precautions taken to minimise measurement uncertainties over the extended time period of the trials are detailed. The field trials involved the use of military training helicopters following selected flight paths around the property while noise level measurements were made internally and externally, before and after replacement of the existing single glazed windows and attenuated ventilation units were installed. The results show that after replacing the main windows with acoustic insulated glazing units, insulation levels of 40dB or above are achieved in most rooms. The results also illustrate the importance of effectively addressing ventilation when windows are replaced. It is concluded that despite complications due to sound flanking and regulatory ventilation, the use of acoustic double-glazing units and properly attenuated ventilation units can effectively reduce helicopter noise in suitable dwellings

Acoustic metamaterials for sound absorption and insulation in buildings

© 2024 The Authors. Published by Elsevier. This is an open access article available under a Creative Commons licence. The published version can be accessed at the following link on the publisher’s website: https://doi.org/10.1016/j.buildenv.2024.111250Despite the emergence of acoustic metamaterials with superior sound absorption and transmission loss, their adoption for building sound insulation has been limited. Sound insulation design in buildings is still informed by the acoustic performance of conventional materials, where the mass law contradicts light weighting when it comes to acoustic design. In any case buildings close to noisy environments such as motorways, railway lines and airports still suffer from significant low frequency noise pollution. Although the limited working bandwidth of acoustic metamaterials is a major issue limiting its application, combining meta-units that interact at various frequencies alongside multi-layer conventional solutions can deliver superior sound insulation in buildings. The review put forwards acoustic metamaterials, specifically emphasising superior sound absorption and transmission/insertion loss as critical properties for effective building sound insulation. The paper reveals a variety of acoustic metamaterials that can be adopted to compliment conventional sound insulation approaches for acoustically efficient building design. The performance of these metamaterials is then explained through their characteristic negative mass density, bulk modulus or repeating or locally resonating microstructure. The review is also extended to air transparent acoustic metamaterials that can be used for sound insulation of building ventilation. Lastly the prospects and challenges regarding the adoption of acoustic metamaterials in building insulation are also discussed. Overall, tuneable, and multifunctional acoustic metamaterials when thoughtfully integrated to building sound insulation can lead to significant acoustic comfort, space-saving and light-weighting.Published versio

A research to reduce interior noise in general aviation airplanes. General aviation interior noise study

The construction, calibration, and properties of a facility for measuring sound transmission through aircraft type panels are described along with the theoretical and empirical methods used. Topics discussed include typical noise source, sound transmission path, and acoustic cabin properties and their effect on interior noise. Experimental results show an average sound transmission loss in the mass controlled frequency region comparable to theoretical predictions. The results also verify that transmission losses in the stiffness controlled region directly depend on the fundamental frequency of the panel. Experimental and theoretical results indicate that increases in this frequency, and consequently in transmission loss, can be achieved by applying pressure differentials across the specimen

New Procedure For Loudness Assesment and Noise Attenuation of Ventilation Kitchen Range Hoods

The Home Ventilating Institute (HVI) created a standard to specify the procedure for sound quality testing of mechanical ventilation equipment. This standard contained a procedure for performance, reliability, and accuracy based on a full assembly loudness assessment. This thesis provides a new generic component loudness assessment procedure that can be utilized to identify and reduce the noise radiating from kitchen range hoods based on an individual component loudness assessment. With these evaluations, design improvements are implemented to help reduce the outgoing noise from the range hood that may cause hearing loss or high stress. Four different range hoods were tested across the 24-1/3 octave frequency bands using the new component loudness assessment procedure. The kitchen range hoods tested include two centrifugal-flow fans and two axial-flow fans for ventilation. Each range hood includes basic component design differences in the damper, grille, and enclosure. The results show that in all but one case the damper caused an increase in the overall loudness by 10% at high speed and as much as 70% at low speed. In addition it has been observed that the addition of the grille can either reduce the loudness or increase the loudness depending on design features. Using the information gathered from the component loudness assessment, practical low-cost noise attenuation techniques are formulated and implemented in order to reduce overall loudness. The primary goal of noise attenuation (or noise reduction) is to diminish the overall loudness to a comfortable level. Using the techniques formulated, vibration and aerodynamic induced noise have been reduced across all speeds of the range hood by as much as 15%. The greatest reduction was observed at high speed with a reduction of 2.17 sones, while mid and low speed were able to archive a reduction of 0.89 sones and 1 sone respectively. The new procedure gives improved insight into individual components contribution to overall loudness, and provides better intuition on how to reduce the outgoing noise. A reduction in noise should improve the sound quality indoors and have a positive effect on consumer health and quality of life

High energy-efficiency buildings

In cold, central European climates, hyper-insulated, heat-conserving buildings have proven a very effective way to reduce current energy consumption to 1/10 th of a traditional house. Using dry, stratified building techniques (Str/En) allows to obtain quite easily the required thermal and acoustical performances, also enhancing the construction process and allowing for the final recycling of the components. In a warmer climate – such as the Italian one – a heat-conserving strategy has to be balanced against the potential overheating problems. Among the possible solutions, the use of building-integrated Phase Change Materials, which could create a " light thermal inertia " (that is, without heavy mass), was also investigated

Optimal learning spaces: design implications for primary schools

Review guide of the design evidence for primary school

A study of the practices and procedures in the kindergartens of Massachusetts,

Thesis (M.A.)--Boston Universit

Interior noise in military helicopters

The Temporary Threshold Shift (TTS) or temporary hearing loss caused by excessive interior noise in military helicopters results in a critical degradation of the acoustically unprotected infantryman\u27s ability to detect the existence or the approach of the enemy by hearing under combat conditions. The overall problem of noise reduction in helicopters consists of: (1) identifying the various noise sources, and (2) employing appropriate noise control techniques. Identification of the source is accomplished by the frequency correlation of 1/10-octave band analysis of the interior sound levels measured within the helicopter cabin with near-field sound generated by the sound sources. Reduction of the overall interior helicopter noise can be accomplished by attenuation or interdiction along the noise \u27\u27path , and/or by redesign of the source to reduce the sound generated in the first place. In the case of the helicopter, attenuation or interdiction of the noise consists of: (1) padding or insulating the source with lightweight absorption materials, (2) vibration isolation of the source, and/or (3) the wearing of ear protection by the passengers. This study proposes the installation of lightweight leaded vinyl sheet as an interior measure until redesign can be accomplished to permit adequate vibration isolation. Ear protection is recommended for all crew and passengers, but it is realized that cost and storage space may be prohibitive --Abstract, page ii